arch/x86/kernel/head_32.S

   1 /*
   2  *
   3  *  Copyright (C) 1991, 1992  Linus Torvalds
   4  *
   5  *  Enhanced CPU detection and feature setting code by Mike Jagdis
   6  *  and Martin Mares, November 1997.
   7  */
   8
   9 .text
  10 #include <linux/threads.h>
  11 #include <linux/init.h>
  12 #include <linux/linkage.h>
  13 #include <asm/segment.h>
  14 #include <asm/page.h>
  15 #include <asm/pgtable.h>
  16 #include <asm/desc.h>
  17 #include <asm/cache.h>
  18 #include <asm/thread_info.h>
  19 #include <asm/asm-offsets.h>
  20 #include <asm/setup.h>
  21 #include <asm/processor-flags.h>
  22
  23 /* Physical address */
  24 #define pa(X) ((X) - __PAGE_OFFSET)
  25
  26 /*
  27  * References to members of the new_cpu_data structure.
  28  */
  29
  30 #define X86             new_cpu_data+CPUINFO_x86
  31 #define X86_VENDOR      new_cpu_data+CPUINFO_x86_vendor
  32 #define X86_MODEL       new_cpu_data+CPUINFO_x86_model
  33 #define X86_MASK        new_cpu_data+CPUINFO_x86_mask
  34 #define X86_HARD_MATH   new_cpu_data+CPUINFO_hard_math
  35 #define X86_CPUID       new_cpu_data+CPUINFO_cpuid_level
  36 #define X86_CAPABILITY  new_cpu_data+CPUINFO_x86_capability
  37 #define X86_VENDOR_ID   new_cpu_data+CPUINFO_x86_vendor_id
  38
  39 /*
  40  * This is how much memory *in addition to the memory covered up to
  41  * and including _end* we need mapped initially.
  42  * We need:
  43  *  - one bit for each possible page, but only in low memory, which means
  44  *     2^32/4096/8 = 128K worst case (4G/4G split.)
  45  *  - enough space to map all low memory, which means
  46  *     (2^32/4096) / 1024 pages (worst case, non PAE)
  47  *     (2^32/4096) / 512 + 4 pages (worst case for PAE)
  48  *  - a few pages for allocator use before the kernel pagetable has
  49  *     been set up
  50  *
  51  * Modulo rounding, each megabyte assigned here requires a kilobyte of
  52  * memory, which is currently unreclaimed.
  53  *
  54  * This should be a multiple of a page.
  55  */
  56 LOW_PAGES = 1<<(32-PAGE_SHIFT_asm)
  57
  58 /*
  59  * To preserve the DMA pool in PAGEALLOC kernels, we'll allocate
  60  * pagetables from above the 16MB DMA limit, so we'll have to set
  61  * up pagetables 16MB more (worst-case):
  62  */
  63 #ifdef CONFIG_DEBUG_PAGEALLOC
  64 LOW_PAGES = LOW_PAGES + 0x1000000
  65 #endif
  66
  67 #if PTRS_PER_PMD > 1
  68 PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PMD) + PTRS_PER_PGD
  69 #else
  70 PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PGD)
  71 #endif
  72 BOOTBITMAP_SIZE = LOW_PAGES / 8
  73 ALLOCATOR_SLOP = 4
  74
  75 INIT_MAP_BEYOND_END = BOOTBITMAP_SIZE + (PAGE_TABLE_SIZE + ALLOCATOR_SLOP)*PAGE_SIZE_asm
  76
  77 /*
  78  * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
  79  * %esi points to the real-mode code as a 32-bit pointer.
  80  * CS and DS must be 4 GB flat segments, but we don't depend on
  81  * any particular GDT layout, because we load our own as soon as we
  82  * can.
  83  */
  84 .section .text.head,"ax",@progbits
  85 ENTRY(startup_32)
  86         /* test KEEP_SEGMENTS flag to see if the bootloader is asking
  87                 us to not reload segments */
  88         testb $(1<<6), BP_loadflags(%esi)
  89         jnz 2f
  90
  91 /*
  92  * Set segments to known values.
  93  */
  94         lgdt pa(boot_gdt_descr)
  95         movl $(__BOOT_DS),%eax
  96         movl %eax,%ds
  97         movl %eax,%es
  98         movl %eax,%fs
  99         movl %eax,%gs
 100 2:
 101
 102 /*
 103  * Clear BSS first so that there are no surprises...
 104  */
 105         cld
 106         xorl %eax,%eax
 107         movl $pa(__bss_start),%edi
 108         movl $pa(__bss_stop),%ecx
 109         subl %edi,%ecx
 110         shrl $2,%ecx
 111         rep ; stosl
 112 /*
 113  * Copy bootup parameters out of the way.
 114  * Note: %esi still has the pointer to the real-mode data.
 115  * With the kexec as boot loader, parameter segment might be loaded beyond
 116  * kernel image and might not even be addressable by early boot page tables.
 117  * (kexec on panic case). Hence copy out the parameters before initializing
 118  * page tables.
 119  */
 120         movl $pa(boot_params),%edi
 121         movl $(PARAM_SIZE/4),%ecx
 122         cld
 123         rep
 124         movsl
 125         movl pa(boot_params) + NEW_CL_POINTER,%esi
 126         andl %esi,%esi
 127         jz 1f                   # No comand line
 128         movl $pa(boot_command_line),%edi
 129         movl $(COMMAND_LINE_SIZE/4),%ecx
 130         rep
 131         movsl
 132 1:
 133
 134 #ifdef CONFIG_PARAVIRT
 135         /* This is can only trip for a broken bootloader... */
 136         cmpw $0x207, pa(boot_params + BP_version)
 137         jb default_entry
 138
 139         /* Paravirt-compatible boot parameters.  Look to see what architecture
 140                 we're booting under. */
 141         movl pa(boot_params + BP_hardware_subarch), %eax
 142         cmpl $num_subarch_entries, %eax
 143         jae bad_subarch
 144
 145         movl pa(subarch_entries)(,%eax,4), %eax
 146         subl $__PAGE_OFFSET, %eax
 147         jmp *%eax
 148
 149 bad_subarch:
 150 WEAK(lguest_entry)
 151 WEAK(xen_entry)
 152         /* Unknown implementation; there's really
 153            nothing we can do at this point. */
 154         ud2a
 155
 156         __INITDATA
 157
 158 subarch_entries:
 159         .long default_entry             /* normal x86/PC */
 160         .long lguest_entry              /* lguest hypervisor */
 161         .long xen_entry                 /* Xen hypervisor */
 162 num_subarch_entries = (. - subarch_entries) / 4
 163 .previous
 164 #endif /* CONFIG_PARAVIRT */
 165
 166 /*
 167  * Initialize page tables.  This creates a PDE and a set of page
 168  * tables, which are located immediately beyond _end.  The variable
 169  * init_pg_tables_end is set up to point to the first "safe" location.
 170  * Mappings are created both at virtual address 0 (identity mapping)
 171  * and PAGE_OFFSET for up to _end+sizeof(page tables)+INIT_MAP_BEYOND_END.
 172  *
 173  * Note that the stack is not yet set up!
 174  */
 175 #define PTE_ATTR        0x007           /* PRESENT+RW+USER */
 176 #define PDE_ATTR        0x067           /* PRESENT+RW+USER+DIRTY+ACCESSED */
 177 #define PGD_ATTR        0x001           /* PRESENT (no other attributes) */
 178
 179 default_entry:
 180 #ifdef CONFIG_X86_PAE
 181
 182         /*
 183          * In PAE mode swapper_pg_dir is statically defined to contain enough
 184          * entries to cover the VMSPLIT option (that is the top 1, 2 or 3
 185          * entries). The identity mapping is handled by pointing two PGD
 186          * entries to the first kernel PMD.
 187          *
 188          * Note the upper half of each PMD or PTE are always zero at
 189          * this stage.
 190          */
 191
 192 #define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
 193
 194         xorl %ebx,%ebx                          /* %ebx is kept at zero */
 195
 196         movl $pa(pg0), %edi
 197         movl %edi, pa(init_pg_tables_start)
 198         movl $pa(swapper_pg_pmd), %edx
 199         movl $PTE_ATTR, %eax
 200 10:
 201         leal PDE_ATTR(%edi),%ecx                /* Create PMD entry */
 202         movl %ecx,(%edx)                        /* Store PMD entry */
 203                                                 /* Upper half already zero */
 204         addl $8,%edx
 205         movl $512,%ecx
 206 11:
 207         stosl
 208         xchgl %eax,%ebx
 209         stosl
 210         xchgl %eax,%ebx
 211         addl $0x1000,%eax
 212         loop 11b
 213
 214         /*
 215          * End condition: we must map up to and including INIT_MAP_BEYOND_END
 216          * bytes beyond the end of our own page tables.
 217          */
 218         leal (INIT_MAP_BEYOND_END+PTE_ATTR)(%edi),%ebp
 219         cmpl %ebp,%eax
 220         jb 10b
 221 1:
 222         movl %edi,pa(init_pg_tables_end)
 223         shrl $12, %eax
 224         movl %eax, pa(max_pfn_mapped)
 225
 226         /* Do early initialization of the fixmap area */
 227         movl $pa(swapper_pg_fixmap)+PDE_ATTR,%eax
 228         movl %eax,pa(swapper_pg_pmd+0x1000*KPMDS-8)
 229 #else   /* Not PAE */
 230
 231 page_pde_offset = (__PAGE_OFFSET >> 20);
 232
 233         movl $pa(pg0), %edi
 234         movl %edi, pa(init_pg_tables_start)
 235         movl $pa(swapper_pg_dir), %edx
 236         movl $PTE_ATTR, %eax
 237 10:
 238         leal PDE_ATTR(%edi),%ecx                /* Create PDE entry */
 239         movl %ecx,(%edx)                        /* Store identity PDE entry */
 240         movl %ecx,page_pde_offset(%edx)         /* Store kernel PDE entry */
 241         addl $4,%edx
 242         movl $1024, %ecx
 243 11:
 244         stosl
 245         addl $0x1000,%eax
 246         loop 11b
 247         /*
 248          * End condition: we must map up to and including INIT_MAP_BEYOND_END
 249          * bytes beyond the end of our own page tables; the +0x007 is
 250          * the attribute bits
 251          */
 252         leal (INIT_MAP_BEYOND_END+PTE_ATTR)(%edi),%ebp
 253         cmpl %ebp,%eax
 254         jb 10b
 255         movl %edi,pa(init_pg_tables_end)
 256         shrl $12, %eax
 257         movl %eax, pa(max_pfn_mapped)
 258
 259         /* Do early initialization of the fixmap area */
 260         movl $pa(swapper_pg_fixmap)+PDE_ATTR,%eax
 261         movl %eax,pa(swapper_pg_dir+0xffc)
 262 #endif
 263         jmp 3f
 264 /*
 265  * Non-boot CPU entry point; entered from trampoline.S
 266  * We can't lgdt here, because lgdt itself uses a data segment, but
 267  * we know the trampoline has already loaded the boot_gdt for us.
 268  *
 269  * If cpu hotplug is not supported then this code can go in init section
 270  * which will be freed later
 271  */
 272
 273 #ifndef CONFIG_HOTPLUG_CPU
 274 .section .init.text,"ax",@progbits
 275 #endif
 276
 277 #ifdef CONFIG_SMP
 278 ENTRY(startup_32_smp)
 279         cld
 280         movl $(__BOOT_DS),%eax
 281         movl %eax,%ds
 282         movl %eax,%es
 283         movl %eax,%fs
 284         movl %eax,%gs
 285 #endif /* CONFIG_SMP */
 286 3:
 287
 288 /*
 289  *      New page tables may be in 4Mbyte page mode and may
 290  *      be using the global pages.
 291  *
 292  *      NOTE! If we are on a 486 we may have no cr4 at all!
 293  *      So we do not try to touch it unless we really have
 294  *      some bits in it to set.  This won't work if the BSP
 295  *      implements cr4 but this AP does not -- very unlikely
 296  *      but be warned!  The same applies to the pse feature
 297  *      if not equally supported. --macro
 298  *
 299  *      NOTE! We have to correct for the fact that we're
 300  *      not yet offset PAGE_OFFSET..
 301  */
 302 #define cr4_bits pa(mmu_cr4_features)
 303         movl cr4_bits,%edx
 304         andl %edx,%edx
 305         jz 6f
 306         movl %cr4,%eax          # Turn on paging options (PSE,PAE,..)
 307         orl %edx,%eax
 308         movl %eax,%cr4
 309
 310         btl $5, %eax            # check if PAE is enabled
 311         jnc 6f
 312
 313         /* Check if extended functions are implemented */
 314         movl $0x80000000, %eax
 315         cpuid
 316         cmpl $0x80000000, %eax
 317         jbe 6f
 318         mov $0x80000001, %eax
 319         cpuid
 320         /* Execute Disable bit supported? */
 321         btl $20, %edx
 322         jnc 6f
 323
 324         /* Setup EFER (Extended Feature Enable Register) */
 325         movl $0xc0000080, %ecx
 326         rdmsr
 327
 328         btsl $11, %eax
 329         /* Make changes effective */
 330         wrmsr
 331
 332 6:
 333
 334 /*
 335  * Enable paging
 336  */
 337         movl $pa(swapper_pg_dir),%eax
 338         movl %eax,%cr3          /* set the page table pointer.. */
 339         movl %cr0,%eax
 340         orl  $X86_CR0_PG,%eax
 341         movl %eax,%cr0          /* ..and set paging (PG) bit */
 342         ljmp $__BOOT_CS,$1f     /* Clear prefetch and normalize %eip */
 343 1:
 344         /* Set up the stack pointer */
 345         lss stack_start,%esp
 346
 347 /*
 348  * Initialize eflags.  Some BIOS's leave bits like NT set.  This would
 349  * confuse the debugger if this code is traced.
 350  * XXX - best to initialize before switching to protected mode.
 351  */
 352         pushl $0
 353         popfl
 354
 355 #ifdef CONFIG_SMP
 356         cmpb $0, ready
 357         jz  1f                          /* Initial CPU cleans BSS */
 358         jmp checkCPUtype
 359 1:
 360 #endif /* CONFIG_SMP */
 361
 362 /*
 363  * start system 32-bit setup. We need to re-do some of the things done
 364  * in 16-bit mode for the "real" operations.
 365  */
 366         call setup_idt
 367
 368 checkCPUtype:
 369
 370         movl $-1,X86_CPUID              #  -1 for no CPUID initially
 371
 372 /* check if it is 486 or 386. */
 373 /*
 374  * XXX - this does a lot of unnecessary setup.  Alignment checks don't
 375  * apply at our cpl of 0 and the stack ought to be aligned already, and
 376  * we don't need to preserve eflags.
 377  */
 378
 379         movb $3,X86             # at least 386
 380         pushfl                  # push EFLAGS
 381         popl %eax               # get EFLAGS
 382         movl %eax,%ecx          # save original EFLAGS
 383         xorl $0x240000,%eax     # flip AC and ID bits in EFLAGS
 384         pushl %eax              # copy to EFLAGS
 385         popfl                   # set EFLAGS
 386         pushfl                  # get new EFLAGS
 387         popl %eax               # put it in eax
 388         xorl %ecx,%eax          # change in flags
 389         pushl %ecx              # restore original EFLAGS
 390         popfl
 391         testl $0x40000,%eax     # check if AC bit changed
 392         je is386
 393
 394         movb $4,X86             # at least 486
 395         testl $0x200000,%eax    # check if ID bit changed
 396         je is486
 397
 398         /* get vendor info */
 399         xorl %eax,%eax                  # call CPUID with 0 -> return vendor ID
 400         cpuid
 401         movl %eax,X86_CPUID             # save CPUID level
 402         movl %ebx,X86_VENDOR_ID         # lo 4 chars
 403         movl %edx,X86_VENDOR_ID+4       # next 4 chars
 404         movl %ecx,X86_VENDOR_ID+8       # last 4 chars
 405
 406         orl %eax,%eax                   # do we have processor info as well?
 407         je is486
 408
 409         movl $1,%eax            # Use the CPUID instruction to get CPU type
 410         cpuid
 411         movb %al,%cl            # save reg for future use
 412         andb $0x0f,%ah          # mask processor family
 413         movb %ah,X86
 414         andb $0xf0,%al          # mask model
 415         shrb $4,%al
 416         movb %al,X86_MODEL
 417         andb $0x0f,%cl          # mask mask revision
 418         movb %cl,X86_MASK
 419         movl %edx,X86_CAPABILITY
 420
 421 is486:  movl $0x50022,%ecx      # set AM, WP, NE and MP
 422         jmp 2f
 423
 424 is386:  movl $2,%ecx            # set MP
 425 2:      movl %cr0,%eax
 426         andl $0x80000011,%eax   # Save PG,PE,ET
 427         orl %ecx,%eax
 428         movl %eax,%cr0
 429
 430         call check_x87
 431         lgdt early_gdt_descr
 432         lidt idt_descr
 433         ljmp $(__KERNEL_CS),$1f
 434 1:      movl $(__KERNEL_DS),%eax        # reload all the segment registers
 435         movl %eax,%ss                   # after changing gdt.
 436         movl %eax,%fs                   # gets reset once there's real percpu
 437
 438         movl $(__USER_DS),%eax          # DS/ES contains default USER segment
 439         movl %eax,%ds
 440         movl %eax,%es
 441
 442         xorl %eax,%eax                  # Clear GS and LDT
 443         movl %eax,%gs
 444         lldt %ax
 445
 446         cld                     # gcc2 wants the direction flag cleared at all times
 447         pushl $0                # fake return address for unwinder
 448 #ifdef CONFIG_SMP
 449         movb ready, %cl
 450         movb $1, ready
 451         cmpb $0,%cl             # the first CPU calls start_kernel
 452         je   1f
 453         movl $(__KERNEL_PERCPU), %eax
 454         movl %eax,%fs           # set this cpu's percpu
 455         movl (stack_start), %esp
 456 1:
 457 #endif /* CONFIG_SMP */
 458         jmp *(initial_code)
 459
 460 /*
 461  * We depend on ET to be correct. This checks for 287/387.
 462  */
 463 check_x87:
 464         movb $0,X86_HARD_MATH
 465         clts
 466         fninit
 467         fstsw %ax
 468         cmpb $0,%al
 469         je 1f
 470         movl %cr0,%eax          /* no coprocessor: have to set bits */
 471         xorl $4,%eax            /* set EM */
 472         movl %eax,%cr0
 473         ret
 474         ALIGN
 475 1:      movb $1,X86_HARD_MATH
 476         .byte 0xDB,0xE4         /* fsetpm for 287, ignored by 387 */
 477         ret
 478
 479 /*
 480  *  setup_idt
 481  *
 482  *  sets up a idt with 256 entries pointing to
 483  *  ignore_int, interrupt gates. It doesn't actually load
 484  *  idt - that can be done only after paging has been enabled
 485  *  and the kernel moved to PAGE_OFFSET. Interrupts
 486  *  are enabled elsewhere, when we can be relatively
 487  *  sure everything is ok.
 488  *
 489  *  Warning: %esi is live across this function.
 490  */
 491 setup_idt:
 492         lea ignore_int,%edx
 493         movl $(__KERNEL_CS << 16),%eax
 494         movw %dx,%ax            /* selector = 0x0010 = cs */
 495         movw $0x8E00,%dx        /* interrupt gate - dpl=0, present */
 496
 497         lea idt_table,%edi
 498         mov $256,%ecx
 499 rp_sidt:
 500         movl %eax,(%edi)
 501         movl %edx,4(%edi)
 502         addl $8,%edi
 503         dec %ecx
 504         jne rp_sidt
 505
 506 .macro  set_early_handler handler,trapno
 507         lea \handler,%edx
 508         movl $(__KERNEL_CS << 16),%eax
 509         movw %dx,%ax
 510         movw $0x8E00,%dx        /* interrupt gate - dpl=0, present */
 511         lea idt_table,%edi
 512         movl %eax,8*\trapno(%edi)
 513         movl %edx,8*\trapno+4(%edi)
 514 .endm
 515
 516         set_early_handler handler=early_divide_err,trapno=0
 517         set_early_handler handler=early_illegal_opcode,trapno=6
 518         set_early_handler handler=early_protection_fault,trapno=13
 519         set_early_handler handler=early_page_fault,trapno=14
 520
 521         ret
 522
 523 early_divide_err:
 524         xor %edx,%edx
 525         pushl $0        /* fake errcode */
 526         jmp early_fault
 527
 528 early_illegal_opcode:
 529         movl $6,%edx
 530         pushl $0        /* fake errcode */
 531         jmp early_fault
 532
 533 early_protection_fault:
 534         movl $13,%edx
 535         jmp early_fault
 536
 537 early_page_fault:
 538         movl $14,%edx
 539         jmp early_fault
 540
 541 early_fault:
 542         cld
 543 #ifdef CONFIG_PRINTK
 544         pusha
 545         movl $(__KERNEL_DS),%eax
 546         movl %eax,%ds
 547         movl %eax,%es
 548         cmpl $2,early_recursion_flag
 549         je hlt_loop
 550         incl early_recursion_flag
 551         movl %cr2,%eax
 552         pushl %eax
 553         pushl %edx              /* trapno */
 554         pushl $fault_msg
 555 #ifdef CONFIG_EARLY_PRINTK
 556         call early_printk
 557 #else
 558         call printk
 559 #endif
 560 #endif
 561         call dump_stack
 562 hlt_loop:
 563         hlt
 564         jmp hlt_loop
 565
 566 /* This is the default interrupt "handler" :-) */
 567         ALIGN
 568 ignore_int:
 569         cld
 570 #ifdef CONFIG_PRINTK
 571         pushl %eax
 572         pushl %ecx
 573         pushl %edx
 574         pushl %es
 575         pushl %ds
 576         movl $(__KERNEL_DS),%eax
 577         movl %eax,%ds
 578         movl %eax,%es
 579         cmpl $2,early_recursion_flag
 580         je hlt_loop
 581         incl early_recursion_flag
 582         pushl 16(%esp)
 583         pushl 24(%esp)
 584         pushl 32(%esp)
 585         pushl 40(%esp)
 586         pushl $int_msg
 587 #ifdef CONFIG_EARLY_PRINTK
 588         call early_printk
 589 #else
 590         call printk
 591 #endif
 592         addl $(5*4),%esp
 593         popl %ds
 594         popl %es
 595         popl %edx
 596         popl %ecx
 597         popl %eax
 598 #endif
 599         iret
 600
 601 .section .cpuinit.data,"wa"
 602 .align 4
 603 ENTRY(initial_code)
 604         .long i386_start_kernel
 605
 606 .section .text
 607 /*
 608  * Real beginning of normal "text" segment
 609  */
 610 ENTRY(stext)
 611 ENTRY(_stext)
 612
 613 /*
 614  * BSS section
 615  */
 616 .section ".bss.page_aligned","wa"
 617         .align PAGE_SIZE_asm
 618 #ifdef CONFIG_X86_PAE
 619 swapper_pg_pmd:
 620         .fill 1024*KPMDS,4,0
 621 #else
 622 ENTRY(swapper_pg_dir)
 623         .fill 1024,4,0
 624 #endif
 625 swapper_pg_fixmap:
 626         .fill 1024,4,0
 627 ENTRY(empty_zero_page)
 628         .fill 4096,1,0
 629 /*
 630  * This starts the data section.
 631  */
 632 #ifdef CONFIG_X86_PAE
 633 .section ".data.page_aligned","wa"
 634         /* Page-aligned for the benefit of paravirt? */
 635         .align PAGE_SIZE_asm
 636 ENTRY(swapper_pg_dir)
 637         .long   pa(swapper_pg_pmd+PGD_ATTR),0           /* low identity map */
 638 # if KPMDS == 3
 639         .long   pa(swapper_pg_pmd+PGD_ATTR),0
 640         .long   pa(swapper_pg_pmd+PGD_ATTR+0x1000),0
 641         .long   pa(swapper_pg_pmd+PGD_ATTR+0x2000),0
 642 # elif KPMDS == 2
 643         .long   0,0
 644         .long   pa(swapper_pg_pmd+PGD_ATTR),0
 645         .long   pa(swapper_pg_pmd+PGD_ATTR+0x1000),0
 646 # elif KPMDS == 1
 647         .long   0,0
 648         .long   0,0
 649         .long   pa(swapper_pg_pmd+PGD_ATTR),0
 650 # else
 651 #  error "Kernel PMDs should be 1, 2 or 3"
 652 # endif
 653         .align PAGE_SIZE_asm            /* needs to be page-sized too */
 654 #endif
 655
 656 .data
 657 ENTRY(stack_start)
 658         .long init_thread_union+THREAD_SIZE
 659         .long __BOOT_DS
 660
 661 ready:  .byte 0
 662
 663 early_recursion_flag:
 664         .long 0
 665
 666 int_msg:
 667         .asciz "Unknown interrupt or fault at EIP %p %p %p\n"
 668
 669 fault_msg:
 670 /* fault info: */
 671         .ascii "BUG: Int %d: CR2 %p\n"
 672 /* pusha regs: */
 673         .ascii "     EDI %p  ESI %p  EBP %p  ESP %p\n"
 674         .ascii "     EBX %p  EDX %p  ECX %p  EAX %p\n"
 675 /* fault frame: */
 676         .ascii "     err %p  EIP %p   CS %p  flg %p\n"
 677         .ascii "Stack: %p %p %p %p %p %p %p %p\n"
 678         .ascii "       %p %p %p %p %p %p %p %p\n"
 679         .asciz "       %p %p %p %p %p %p %p %p\n"
 680
 681 #include "../../x86/xen/xen-head.S"
 682
 683 /*
 684  * The IDT and GDT 'descriptors' are a strange 48-bit object
 685  * only used by the lidt and lgdt instructions. They are not
 686  * like usual segment descriptors - they consist of a 16-bit
 687  * segment size, and 32-bit linear address value:
 688  */
 689
 690 .globl boot_gdt_descr
 691 .globl idt_descr
 692
 693         ALIGN
 694 # early boot GDT descriptor (must use 1:1 address mapping)
 695         .word 0                         # 32 bit align gdt_desc.address
 696 boot_gdt_descr:
 697         .word __BOOT_DS+7
 698         .long boot_gdt - __PAGE_OFFSET
 699
 700         .word 0                         # 32-bit align idt_desc.address
 701 idt_descr:
 702         .word IDT_ENTRIES*8-1           # idt contains 256 entries
 703         .long idt_table
 704
 705 # boot GDT descriptor (later on used by CPU#0):
 706         .word 0                         # 32 bit align gdt_desc.address
 707 ENTRY(early_gdt_descr)
 708         .word GDT_ENTRIES*8-1
 709         .long per_cpu__gdt_page         /* Overwritten for secondary CPUs */
 710
 711 /*
 712  * The boot_gdt must mirror the equivalent in setup.S and is
 713  * used only for booting.
 714  */
 715         .align L1_CACHE_BYTES
 716 ENTRY(boot_gdt)
 717         .fill GDT_ENTRY_BOOT_CS,8,0
 718         .quad 0x00cf9a000000ffff        /* kernel 4GB code at 0x00000000 */
 719         .quad 0x00cf92000000ffff        /* kernel 4GB data at 0x00000000 */